1. Field of the Invention
This invention relates to a print hammer assembly and the actuating mechanism for the print hammer assembly of a line impact printer. More particularly, this inventions relates to a novel movable carriage having a plurality of print hammers mounted thereon. Each movable print hammer is adapted to scan a plurality of column positions.
2. Description of the Prior Art
Prior art single element typewriters and single element printers have been provided with spherical balls, cylindrical drums, cylindrical wheels and annular daisy wheel shaped hammers having a plurality of characters thereon. Such typewriters and printers are capable of typing or printing long lines of characters one column at a time. The desired character of the character carrying element is designed to strike a paper medium so as to leave a character impression thereon.
Impact printers may also employ moving character bearing elements, however, the moving character or font is placed in a position of the backing roll of a typewriter behind the paper to be imprinted with the character. A plane face printing hammer is positioned on the opposite side of the paper and is adapated to strike the paper and press it against the character or font.
Single element typewriters and printers have a relatively heavy amount of moving parts and are limited to around 300 words per minute. Impact line printers having moving characters or font in the form of drums, bands, chains or bars may employ print hammers at every column position, thus substantially increasing the speed of printing a line of characters. High speed impact printers having a print hammer at each column position are capable of printing up to 4,000 lines per minute.
Heretofore, impact printers have employed print hammers which print more than one column position. Also, impact printers have employed print hammers which were mobilized to scan a complete line of column positions. Impact printers have employed a plurality of fixed print hammers which are arranged to print more than a single column of characters in a line printer. In this latter type of printer, the head of the print hammer is designed to span more than one column position and is then selectively actuated to print one of the desired column positions.
High speed impact printers gain most of their speed advantage by reducing the mass of the print hammers to a minimum and by employing high speed fixedly mounted actuating mechanisms as separate elements. If the parts or elements of the actuating mechanism are physically connected to or made part of the print hammers, the effective mass of the print hammers is increased which ordinarily results in a decrease in printing speed. To overcome the increase in effective mass of parts connected to the actuating mechanisms, the return springs and size of the actuators must ordinarily be increased which further increases the mass of the moving system.
Heretofore, single element typewriters and printers as well as single element moving impact printing actuators have been employed in low speed printing mechanisms. Single element typewriters and printers are relatively inexpensive when compared to high speed printers.
It would be desirable to provide a medium or high speed impact printer at a cost comparable to single element typewriters, single element printers and single element moving impact printers.